As a technique of this type, Patent Literature 1 discloses an LED substrate electric connection device 102 that electrically and mechanically connects an LED substrate 100 and an LED substrate 101 to each other as shown in FIG. 15 of this application. The LED substrate electric connection device 102 includes a first connector 103 which is mounted on the LED substrate 100, and a second connector 104 which is mounted on the LED substrate 101. The first connector 103 includes a first terminal 105 which is elongated and extends along a direction parallel to the surface of the LED substrate 100. The second connector 104 includes a second housing 106 having an opening into which the first terminal 105 of the first connector 103 is inserted.